The disclosure of Japanese Patent Application No. 2000-383668 filed on Dec. 18, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a braking control method and apparatus for a vehicle such as a motor vehicle or the like. More particularly, the invention relates to a braking control method and apparatus that controls the braking force based on the amount of braking operation performed on a brake operating member by an operating person.
2. Description of Related Art
A conventionally known braking control apparatus for a vehicle such as a motor vehicle or the like is a braking control apparatus described in, for example, Japanese Patent Application Laid-Open No. 2000-25605, which is designed to operate in a braking control mode in which braking force generating means for each wheel is controlled by electric-type braking control means based on the amount of braking operation of a driver performed on a brake operating member, such as a brake pedal or the like, and in a driver braking mode in which braking force is generated by transferring the operating force exerted on the brake operating member by the driver to the braking force generating means. The mode is shifted from the braking control mode to the driver braking mode if an abnormality occurs in an electric energy supply apparatus for supplying electric energy.
In general, in a braking control apparatus designed with the braking control mode and the driver braking mode, the ratio of the braking force to the amount of driver""s braking operation is set to a higher value for the braking control mode than for the driver braking mode. Therefore, the conventional braking control apparatus as described above have the following problem. That is, if an abnormality occurs in the electric energy supply apparatus, the mode is switched from the braking control mode to the driver braking mode, so that the ratio of the braking force to the amount of driver""s braking operation, that is, the braking effectiveness, sharply drops. Therefore, the ratio of the vehicle deceleration to the amount of driver""s braking operation sharply reduces, thereby causing the driver to experience an uncomfortable feeling.
It is an object of the invention to prevent a sharp reduction in the ratio of the amount of a driver""s braking operation to the vehicle deceleration and therefore a discomfort to the driver by preventing a sharp drop in the ratio of the braking force to the amount of the driver""s braking operation when a mode is switched from a controlled braking mode to a driver braking mode.
A first aspect of the invention is a braking control method and apparatus of a vehicle including a controller having a controlled braking mode in which a target amount of braking control is calculated based on an amount of braking operation performed by a driver on a braking member and a valve is controlled based on the target amount of braking control, and a driver braking mode in which a braking force is generated by transferring an operating force exerted on the braking member by the driver to the valve. The controller predicts an abnormal state in which continuation of a control of the braking force in the controlled braking mode is impossible, and switches from the controlled braking mode to the driver braking mode if the abnormal state is predicted. The controller adjusts a ratio of the braking force generated by the valve to the amount of braking operation of the driver closer to a ratio set for the driver braking mode before the controlled braking mode is switched to the driver braking mode.
According to the first aspect of the invention, if an abnormal state in which the control of the braking force in the controlled braking mode cannot be continued is predicted, the controlled braking mode is switched to the driver braking mode by the controller. However, before the switch from the controlled braking mode to the driver braking mode, the ratio of the braking force generated by the controller to the amount of braking operation of the driver is adjusted closer to the ratio set for the driver braking mode by the controller. Therefore, the braking control apparatus reliably prevents an occurrence where the ratio of the braking force generated by the valve to the amount of braking operation of the driver sharply falls at the time of switching from the controlled braking mode to the driver braking mode.
A second aspect of the invention is a braking control method and apparatus of a vehicle including a controller having a controlled braking mode in which a target amount of braking control is calculated based on an amount of braking operation performed by a driver on a braking member and valves are controlled based on the target amount of braking control, and a driver braking mode in which a braking force is generated by transferring an operating force exerted on the braking member by the driver to the valves. At the time of an abnormal state in which continuation of a control of the braking force in the controlled braking mode is impossible, the braking control apparatus switches the controlled braking mode to the driver braking mode by the controller. The controller predicts an abnormal state. The controller adjusts the ratio of the braking force generated by the valves to the amount of braking operation of the driver closer to the ratio set for the controlled driver mode if the abnormal state is predicted during the controlled braking mode.
According to the second aspect of the invention, if an abnormal state in which the control of the braking force in the controlled braking mode cannot be continued is predicted, the ratio of the braking force generated by the valves to the amount of braking operation of the driver is adjusted closer to the ratio set for the driver braking mode by the controller. Therefore, if the controlled braking mode is switched to the driver braking mode upon occurrence of the abnormal state in which the control of the braking force in the controlled braking mode cannot be continued, the ratio of the braking force generated by the valves to the amount of braking operation of the driver is reliably prevented from sharply falling.
In the first and second aspects, the controller may adjust the ratio of the braking force generated by the valves to the amount of braking operation of the driver closer to the ratio set for the driver braking mode by reducing a ratio of the target amount of braking control to the amount of braking operation of the driver.
It is possible to easily and reliably adjust the ratio of the braking force generated by the valves to the amount of braking operation of the driver closer to the ratio set for the driver braking mode by adjusting the ratio of the braking force generated by the valves to the amount of braking operation of the driver closer to the ratio set for the driver braking mode by reducing the ratio of the target amount of braking control to the amount of braking operation of the driver. To the contrary, it is difficult to adjust the ratio of the braking force generated where the amount of braking operation caused by the driver serves as a basis for calculating the target amount of braking control, or a case where the braking force generated by the valves is reduced for correction.
In the second aspect of the invention, the controller can operate on an electric energy supplied from an electric energy source, and the controller can predict an abnormality in the electric energy source.
The controller operates on electric energy supplied from the electric energy source and can predict an abnormality in the electric energy source. The ratio of the braking force generated by the valves to the amount of braking operation of the driver can be reliably adjusted by the controller closer to the ratio set for the driver braking mode even if the braking control mode is switched to the driver braking mode due to an abnormality in the electric energy source.
Furthermore, the electric energy source may have a first electric energy source and a second electric energy source, and the controller may predict an abnormality in the electric energy source by detecting a dangerous condition of one of the first electric energy source and the second electric energy source losing a function thereof.
If an abnormality in the electric energy source is detected by detecting a danger of one of the first and second electric energy sources losing a function thereof, the ratio of the braking force generated by the valves to the amount of braking operation of the driver can be adjusted closer to the ratio set for the driver braking mode even if the controlled braking mode is switched to the driver braking mode due to the other one of the electric energy sources losing its function as well.